Selective signaling system



152mm s. K. THOMPSON SELECTIVE. SIGNALING SYSTEM Filed Dec. 5, 1923 A TTORNEY have been illustrated as embodied in: certain specific forms which have been deemed desirable, it, will .beunderstood that they are capable ofembodiment in many and widely varied forms without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

L'In a selective signaling system, line polarized periodic current upon. said line to operate said responsive means, and electrical discharge tubes in series with the signaling devices, said tubes being of such construc tion that they willpresent an open circuit to the direct current for operating said responsive means and will break down and allow to pass through them the higher voltage polarized periodic current used to operate said signaling devices.

2. In a telephone system comprising a central station having line and supervisory signals, line conductors, a plurality of substations bridged across said conductors, a source of direct current for said line and supervisory signals and for said stations, a plurality of sources of polarized periodic current of different-frequencies, a signaling] device associated with each station in bridged relation to said conductors, certain of said signaling devices being responsive to polarized periodic current of one frequency and others to current of another frequency, and an electrical discharge tube in series with each of said signaling devices rect current below a critical voltage and 'will break down and thereby permit the passage of polarized periodic current of higher voltage. I

3. In a telephone system comprising a central ofiice, line and supervisory signals thereat, a source of direct current for said signals. line conductors, a plurality of biased signaling devices bridged across said conductors, certain of said devices being responsive to currentof one frequency and others to current of another frequency, electrical discharge tubes in series with said signaling devices, a plurality of sources of polarized periodic current for said signaling system, certain of said sources being of one frequency undother of said sources being of another frequency, said electrical discharge tubes being of such construction that they will present a substantially open circuit impedance to the direct current used for operating said line and supervisory signals and will. break down and allow to pass through them the current used to operate the biased signaling devices.

4 In a selective signaling system, biased signaling devices associated therewith, one pair of said signaling devices being directly selective to one frequency and the other pair being selective to another frequency, and resywetive electrical discharge tubes in series with said devices, said tubes being of such construction that they will present a substantially open circuit impedance to direct current alnlwill break down and allow to pass through them the polarized periodic current of higher voltage used to operate the biased signaling (lGVlCGS.

In testiinonv whereof, I have signed my name to this specification this 30th day of November, 1923.

GEORGE K. THOMPSON. 

